$A$ transformer has an efficiency of $80 \%$ and works at $10 \ V$ and $4 \ kW$. If the secondary voltage is $240 \ V$, then the current in the secondary coil is: (in $A$)

Write the principle of a transformer.

$A$ step-down transformer converts transmission line voltage from $11000 \, V$ to $220 \, V$. The primary of the transformer has $6000 \, \text{turns}$ and the efficiency of the transformer is $60 \%$. If the output power is $9 \, kW$, then the input power will be ........ $kW$.

The number of turns in the primary and secondary coils of a transformer are $50$ and $200$ respectively. If the current in the primary coil is $4 \,A$, then the current in the secondary coil is: (in $\,A$)

$A$ step-down transformer is connected to a $2400\,V$ line, and $80\,A$ of current is found to flow in the output load. The ratio of the turns in the primary and secondary coil is $20:1$. If the transformer efficiency is $100\%$, then the current flowing in the primary coil will be......$A$.

$A$ power transmission line feeds input power at $2.3 \text{ kV}$ to a step-down transformer with its primary winding having $3000$ turns. The output power is delivered at $230 \text{ V}$ by the transformer. The current in the primary of the transformer is $5 \text{ A}$ and its efficiency is $90 \%$. The winding of the transformer is made of copper. The output current of the transformer is . . . . . . $A$.